Path: utzoo!attcan!uunet!snorkelwacker!usc!samsung!noose.ecn.purdue.edu!mentor.cc.purdue.edu!mace.cc.purdue.edu!dil
From: dil@mace.cc.purdue.edu (Perry G Ramsey)
Newsgroups: sci.space.shuttle
Subject: Re: center engine out
Summary: Inboard engine did go out to reduce acceleration
	 It didn't spin up like a discus hurler
Keywords: Apollo
Message-ID: <5556@mace.cc.purdue.edu>
Date: 19 Sep 90 17:38:00 GMT
References: <7285@eos.UUCP>
Distribution: sci.
Organization: Department of Earth and Atmospheric Sciences
Lines: 26

In article <7285@eos.UUCP>, brody@eos.UUCP (Adam R. Brody) writes:
> middle engine of the S-1C first stage goes out while the surrounding four
> burn until completion.  The same thing occurs with the SII second stage at
> 3:30.  Why is this?

The inboard engines of the Saturn V shut down to reduce acceleration.
As the fuel burned, the stack got lighter, so the same thrust resulted
in higher acceleration.  To keep the loads down, they shut down one
engine.  The engines also became more efficient as the ambient pressure
went down, so the raw thrust increased.  Note that the Shuttle solids
have the propellant properties tailored to make the thrust go down
as the vehicle gets higher.


> The book also mentioned that Apollo took 1.5 orbits around the Earth before
> TLI to gain momentum much like a discus thrower.  Can somebody explain this?
> Can it be like a gravity assist to another planet?

The parking orbit was just to check out the vehicle before proceeding to
the moon.  There was no momentum gain.

-- 
Perry G. Ramsey           Department of Earth and Atmospheric Sciences
perryr@vm.cc.purdue.edu   Purdue University
dil@mace.cc.purdue.edu    We've looked at clouds from ten sides now, 
			  And we REALLY don't know clouds, at all.